The present invention relates to a grip device and, more particularly, to a grip device for grasping and conveying a sheet-like object such as, for example, a semiconductor wafer.
With regard to the handling of sheet-like objects to be grasped, such as, for example, semiconductor wafers, various measures have been proposed in, for example, Japanese Patent Application Laid Open Nos. 58-75844 and 58-155736, which include a system for handling the object by vacuum suction and a system for grasping an outer peripheral edge of the object for the purpose of preventing deleterious or harmful matters such as, for example, dust from adhering to the semiconductor wafer.
Since the grip devices of the above proposed type include slide portions such as, for example, a pin coupling an a sliding surface which form sources of contamination such as dust, in actual practice, the proposed grip devices cannot maintain high degrees of cleanliness or freedom from contamination of the surfaces of the semiconductor wafers.
In, for example, a publication entitled "Report of Investigation and Researches on Developments of Applications of Shape Memory Alloys'", pages 110-111, Osaka Science and Technology Center in Japan, Committee on Investigation and Researches on Developments of Applications of Shape Memory Alloys, March, 1983, a grip device for grasping an object in ordinary atmosphere has been proposed, which grip device opens and closes grip members due to a combination between a bias spring and a shape memory alloy member in the form of a coiled spring. With this proposed grip device, the structure around the shape memory alloy member, formed into the coiled spring, is complicated and the use of the grip device in a clean environment is not taken into consideration. Moreover, since the shape of the memory alloy is in the form of a coiled spring, the cooling efficiency thereof is inferior, and the opening and closing operation of the grip members of the grip device is relatively slow so that the device is not suitable for the handling of objects requiring high speed operation.
The aim underlying the present invention essentially resides in providing a grip device for producing little, if any, contaminants or deleterious substances such as, for example, dust, with the grip device including grip members which open and close with high accuracy and with a good response time.
In accordance with advantageous features of the present invention, a grip device is provided wherein an outer peripheral edge of a flat objected to be grasped is gripped at a place to be gripped, with the grip members of the grip device being attached to a base of the grip device by elastic members for urging the corresponding grip members in an opening direction or a closing direction. Additionally, a linear or flat driver means, fashioned of a shape memory alloy, is disposed across the grip members of the grip device.
By virtue of the features of the present invention, it is possible to dispense with the provision of any slide portions so that a grip device producing little if any contaminants such as dust can readily be realized. Moreover, since the shape memory alloy, serving as the driving means of the grip members, is linear or flat, heating and cooling speeds thereof become relatively high so that the response time or responsiveness of the opening and closing operations of the grip members can be significantly enhanced.